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    <title>Document</title>
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<body>
    <script>
let arr1=[1,2,3]
let arr2=[4,5,6]
let  arr3=arr1.concat(arr2)

console.log(arr3)


//  new  Set()


let  arr4=[1,2,3,1,2,1,2,4,3,2,1]

//方法一
// let newObj={}; 
// let newArr1= arr4.filter((item,index)=>{
  
    
//     if(!newObj[item]) {
//         newObj[item]=1   
//           return true
//     }    
// })

// console.log(newObj)
// console.log(newArr1)

// 方法二

  let  newArr = [...new Set(arr4)]

  console.log(newArr)


  





















    </script>
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